1. Field of the Invention
The invention relates to a process for the manufacture of yarn provided with a superabsorbent material.
Said yarn can be utilized in cables, more particularly optical communications cables, in this way functioning simultaneously as reinforcing member and as water blocking agent.
A yarn provided with a superabsorbent material and the manufacture of such a yarn are known from European Patent Applications 482,703 and 351,100, U.S. Pat. No. 5,635,569, and PCT application WO 93/18223. According to these publications yarns are impregnated with a superabsorbent material in a water-oil emulsion. After being impregnated the treated yarn is dried, so that a film is formed in and around the yarn's interstices. The resulting product is used as reinforcing material for the manufacture of a communications cable with water blocking properties.
However, there are drawbacks to the above-mentioned methods of applying a superabsorbent material to a cable or yarn surface. A major disadvantage is the release of organic materials, in particular isohexadecane, during the process of drying the yarn. Such organic materials form an unacceptable environmental burden, and isohexadecane must be eliminated by burning or by treatment in a waste gas unit. Such step requires expensive equipment and uses substantial amounts of energy. It is therefore an advantage to eliminate the use of water-oil emulsions, and to apply materials which are water soluble.
The drawback to impregnating an aramid yarn with a superabsorbent material dispersed in an aqueous system is that, due to the superabsorbent material's high viscosity enhancing action, uniform feeding of it is extremely difficult, if not impossible. Further, on account of the limited concentration of superabsorbent material in the impregnating liquid only a small quantity of it can be applied to the yarn per treatment. Another drawback to this method is that the comparatively large amount of impregnating liquid which is applied to the yarn with the superabsorbent material has to be removed again by evaporation.